Diary Reveals Accused Killer’s Premeditated Plan to Assassinate UnitedHealthcare CEO in Anti-Insurance Industry Attack

Luigi Mangione, charged with murder in the death of UnitedHealthcare CEO Brian Thompson, appears in a New York City court on February 21

Newly disclosed diary entries written by Luigi Mangione, the man accused of assassinating UnitedHealthcare CEO Brian Thompson, detail his calculated motivations and long-standing resentment toward the American health insurance industry, according to a recent court filing.

Mangione, 27, was arrested on December 9, 2024, at a McDonald’s in Altoona, Pennsylvania, just hours after allegedly shooting Thompson on a Manhattan sidewalk. Thompson had been en route to a hotel hosting his company’s investor conference. The suspect, now charged with first-degree murder in furtherance of terrorism, pleaded not guilty to both state and federal charges.

In a red notebook recovered at the time of his arrest, Mangione expressed deep frustration with corporate health care and outlined a plan he believed would expose what he called the "greed" and "abuse" of the industry. His August 2024 diary entries show increasing clarity and confidence in his intentions, stating: “I finally feel confident about what I will do... The target is insurance. It checks every box.”

Mangione, once a high school valedictorian and Ivy League graduate from a wealthy family, vanished from public view in the summer of 2024. Friends and online followers expressed concern over his sudden disappearance. During that time, his private writings focused obsessively on his disdain for the health insurance system and how to carry out a targeted, public act to gain sympathy and attention without harming bystanders.

In an October 2024 entry, he rejected the idea of using a bomb, writing, “Bombs = terrorism… [they] appear the unjustified anger of someone who simply got sick/had bad luck.” He argued that a bombing would alienate public support and compared indiscriminate violence unfavorably to the methodical targeting of corporate figures. He referenced infamous figures like the Unabomber to illustrate what he viewed as failed tactics, writing that “by committing indiscriminate atrocities he becomes a monster… [and] his ideas those of a monster.”

Prosecutors say Mangione’s writings and alleged use of a ghost gun with shell casings engraved with the words “delay,” “deny,” and “depose”—a reference to common criticisms of insurance industry practices—underscore the ideological motivation behind the killing. They argue that the murder of Thompson was meant to send a broader message: to intimidate insurance executives, disrupt financial investment in the industry, and incite public outrage over perceived corporate greed.

Authorities claim Mangione specifically targeted UnitedHealthcare, not because of any personal relationship—he was not insured by the company between 2014 and 2024—but because of its status as the nation’s largest health insurer.

Since the shooting, Mangione has attracted a cult-like following online, with some supporters viewing him as a symbol of resistance against the for-profit health care system. A legal defense fund in his name has raised over $1 million.

The fallout from the assassination has been significant. UnitedHealthcare employees and executives reported widespread fear, prompting the company to remove photos of leadership from its website and advise staff against wearing branded clothing. Security was increased at the company’s headquarters and at regional offices, and at least 40 executives were assigned personal protection. One executive dyed her hair and relocated after receiving repeated threats.

Physicians reportedly asked to remain anonymous on denial letters out of fear for their safety, and some resigned from their positions. Executives from other insurance companies, including Emblem Health, were also targeted. Posters appeared outside corporate offices reading “Health Care CEOs should not feel safe. Deny, Defend, Depose.”

Prosecutors argue that Mangione’s actions sparked a wave of threats against health insurance professionals and escalated public hostility toward the industry. An NYPD intelligence report described the incident as a potential signal of heightened threats facing corporate executives in the sector.

The court filing asserts that Mangione’s attack was not an impulsive act, but a premeditated, ideologically motivated effort “to broadcast his message of ideological intimidation as broadly and loudly as possible.”